The optical scanning head includes at least one trio of light emitting diodes arranged so the LEDs emit light at different angles to create a fan of light. An optical module includes a light shield or "dark room" and a lens/filter assembly which provides control of the depth of focus of the scanner....http://www.google.fr/patents/US5532467?utm_source=gb-gplus-shareBrevet US5532467 - Optical scanning head
